Supporting high speeds in vehicle-to-vehicle communication

ABSTRACT

During device-to-device communication between two devices, a communication transmitted from a first UE to a second UE may not be reliably received by the second UE if the first UE is traveling at high speed. Therefore, a travel speed of a transmitting UE may be considered in determining a transmission configuration. According to an aspect, the UE may determine a travel speed of the UE. The UE may determine, based on the travel speed of the UE, a transmission configuration of the UE for device-to-device communication. The UE may transmit the device-to-device communication based on the transmission configuration.

CROSS-REFERENCE TO RELATED APPLICATION(S)

This application is a divisional application of U.S. Non-provisionalapplication Ser. No. 15/365,384, entitled “SUPPORTING HIGH SPEEDS INVEHICLE-TO-VEHICLE COMMUNICATION” and filed on Nov. 30, 2016, whichclaims the benefit of U.S. Provisional Application Ser. No. 62/311,057,entitled “SUPPORTING HIGH SPEEDS IN LTE-D BASED V2V” and filed on Mar.21, 2016 and U.S. Provisional Application Ser. No. 62/331,754, entitled“SUPPORTING HIGH SPEEDS IN VEHICLE-TO-VEHICLE COMMUNICATION” and filedon May 4, 2016, of which are expressly incorporated by reference hereinin their entirety.

BACKGROUND Field

The present disclosure relates generally to communication systems, andmore particularly, to vehicle-to-vehicle communications among devices.

Background

Wireless communication systems are widely deployed to provide varioustelecommunication services such as telephony, video, data, messaging,and broadcasts. Typical wireless communication systems may employmultiple-access technologies capable of supporting communication withmultiple users by sharing available system resources. Examples of suchmultiple-access technologies include code division multiple access(CDMA) systems, time division multiple access (TDMA) systems, frequencydivision multiple access (FDMA) systems, orthogonal frequency divisionmultiple access (OFDMA) systems, single-carrier frequency divisionmultiple access (SC-FDMA) systems, and time division synchronous codedivision multiple access (TD-SCDMA) systems.

These multiple access technologies have been adopted in varioustelecommunication standards to provide a common protocol that enablesdifferent wireless devices to communicate on a municipal, national,regional, and even global level. An example telecommunication standardis Long Term Evolution (LTE). LTE is a set of enhancements to theUniversal Mobile Telecommunications System (UMTS) mobile standardpromulgated by Third Generation Partnership Project (3GPP). LTE isdesigned to support mobile broadband access through improved spectralefficiency, lowered costs, and improved services using OFDMA on thedownlink, SC-FDMA on the uplink, and multiple-input multiple-output(MIMO) antenna technology. However, as the demand for mobile broadbandaccess continues to increase, there exists a need for furtherimprovements in LTE technology. These improvements may also beapplicable to other multi-access technologies and the telecommunicationstandards that employ these technologies.

Device-to-device (D2D) communication over a licensed spectrum has beenunder development to provide a way for a user equipment to directlycommunicate with another user equipment in LTE. Improvements are beingcontinuously made to provide reliable device-to-device communicationover the licensed spectrum in various circumstances

SUMMARY

The following presents a simplified summary of one or more aspects inorder to provide a basic understanding of such aspects. This summary isnot an extensive overview of all contemplated aspects, and is intendedto neither identify key or critical elements of all aspects nordelineate the scope of any or all aspects. Its sole purpose is topresent some concepts of one or more aspects in a simplified form as aprelude to the more detailed description that is presented later.

During D2D communication between two devices, a communicationtransmitted from a first UE to a second UE may not be reliably receivedby the second UE if the first UE is traveling at high speed. Therefore,the travel speed of a transmitting UE may be considered in determiningthe transmission configuration of the transmitting UE. In addition, whena UE receives control channel and data from other UEs, decoding of thecontrol channel may be complex. Thus, an approach to reduce thecomplexity in decoding the control channel may be desirable.

In an aspect of the disclosure, a method, a computer-readable medium,and an apparatus for wireless communication are provided. The apparatusmay be a UE. The apparatus may determine a travel speed of the UE. Theapparatus may determine, based on the travel speed of the UE, atransmission configuration of the UE for device-to-device communication.The device-to-device communication may be over a licensed or unlicensedspectrum. The apparatus may transmit the device-to-device communicationbased on the transmission configuration.

In another aspect of the disclosure, a method, a computer-readablemedium, and an apparatus for wireless communication are provided. Theapparatus may be a UE. The apparatus may receive a communication from atransmitting UE via device-to-device communication. The device-to-devicecommunication may be over a licensed or unlicensed spectrum. Theapparatus may determine a corresponding set of scheduling assignment(SA) resources used to receive the communication from the transmittingUE among a plurality of sets of SA resources. The available SA resourcesmay be divided into the plurality of sets of SA resources based on typesof SA transmission configurations. The apparatus may decode an SA basedon the communication within the corresponding set of SA resources. Theapparatus may determine a data transmission configuration based on theSA within the corresponding set of SA resources. The apparatus mayreceive data from the transmitting UE based on the data transmissionconfiguration.

In yet another aspect of the disclosure, a method, a computer-readablemedium, and an apparatus for wireless communication are provided. Theapparatus may be a UE. The apparatus may determine to enable grouphopping for a plurality of demodulation reference signal (DM-RS)sequences associated with a control channel for device-to-devicecommunication. The plurality of DM-RS sequences may be carried on aplurality of DM-RS symbols within the control channel of a subframe. Theapparatus may determine the plurality of DM-RS sequences by applying agroup hopping pattern to the plurality of DM-RS symbols. The apparatusmay transmit or receive a scheduling assignment for the device-to-devicecommunication with the plurality of DM-RS sequences.

To the accomplishment of the foregoing and related ends, the one or moreaspects comprise the features hereinafter fully described andparticularly pointed out in the claims. The following description andthe annexed drawings set forth in detail certain illustrative featuresof the one or more aspects. These features are indicative, however, ofbut a few of the various ways in which the principles of various aspectsmay be employed, and this description is intended to include all suchaspects and their equivalents.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a diagram illustrating an example of a wireless communicationssystem and an access network.

FIGS. 2A, 2B, 2C, and 2D are diagrams illustrating LTE examples of a DLframe structure, DL channels within the DL frame structure, an UL framestructure, and UL channels within the UL frame structure, respectively.

FIG. 3 is a diagram illustrating an example of an evolved Node B (eNB)and user equipment (UE) in an access network.

FIG. 4 is a diagram of an example of a device-to-device communicationssystem.

FIG. 5 is a diagram illustrating an example of a V2V communicationsystem.

FIG. 6 is an example plot illustrating an error rate experienced by a UEin various situations.

FIG. 7 is an example diagram illustrating SA resources, according to anaspect of the disclosure.

FIG. 8 is a flowchart of a method of wireless communication, accordingto an aspect of the disclosure.

FIG. 9 is a flowchart of a method of wireless communication, accordingto an aspect of the disclosure.

FIG. 10 is a diagram illustrating an example of enabling group hoppingfor DM-RS symbols within a subframe.

FIG. 11 is a flowchart of a method of wireless communication inaccordance with an aspect of the disclosure.

FIG. 12 is a conceptual data flow diagram illustrating the data flowbetween different means/components in an exemplary apparatus.

FIG. 13 is a diagram illustrating an example of a hardwareimplementation for an apparatus employing a processing system.

DETAILED DESCRIPTION

The detailed description set forth below in connection with the appendeddrawings is intended as a description of various configurations and isnot intended to represent the only configurations in which the conceptsdescribed herein may be practiced. The detailed description includesspecific details for the purpose of providing a thorough understandingof various concepts. However, it will be apparent to those skilled inthe art that these concepts may be practiced without these specificdetails. In some instances, well known structures and components areshown in block diagram form in order to avoid obscuring such concepts.

Several aspects of telecommunication systems will now be presented withreference to various apparatus and methods. These apparatus and methodswill be described in the following detailed description and illustratedin the accompanying drawings by various blocks, components, circuits,processes, algorithms, etc. (collectively referred to as “elements”).These elements may be implemented using electronic hardware, computersoftware, or any combination thereof. Whether such elements areimplemented as hardware or software depends upon the particularapplication and design constraints imposed on the overall system.

By way of example, an element, or any portion of an element, or anycombination of elements may be implemented as a “processing system” thatincludes one or more processors. Examples of processors includemicroprocessors, microcontrollers, graphics processing units (GPUs),central processing units (CPUs), application processors, digital signalprocessors (DSPs), reduced instruction set computing (RISC) processors,systems on a chip (SoC), baseband processors, field programmable gatearrays (FPGAs), programmable logic devices (PLDs), state machines, gatedlogic, discrete hardware circuits, and other suitable hardwareconfigured to perform the various functionality described throughoutthis disclosure. One or more processors in the processing system mayexecute software. Software shall be construed broadly to meaninstructions, instruction sets, code, code segments, program code,programs, subprograms, software components, applications, softwareapplications, software packages, routines, subroutines, objects,executables, threads of execution, procedures, functions, etc., whetherreferred to as software, firmware, middleware, microcode, hardwaredescription language, or otherwise.

Accordingly, in one or more example embodiments, the functions describedmay be implemented in hardware, software, or any combination thereof. Ifimplemented in software, the functions may be stored on or encoded asone or more instructions or code on a computer-readable medium.Computer-readable media includes computer storage media. Storage mediamay be any available media that can be accessed by a computer. By way ofexample, and not limitation, such computer-readable media can comprise arandom-access memory (RAM), a read-only memory (ROM), an electricallyerasable programmable ROM (EEPROM), optical disk storage, magnetic diskstorage, other magnetic storage devices, combinations of theaforementioned types of computer-readable media, or any other mediumthat can be used to store computer executable code in the form ofinstructions or data structures that can be accessed by a computer.

FIG. 1 is a diagram illustrating an example of a wireless communicationssystem and an access network 100. The wireless communications system(also referred to as a wireless wide area network (WWAN)) includes basestations 102, UEs 104, and an Evolved Packet Core (EPC) 160. The basestations 102 may include macro cells (high power cellular base station)and/or small cells (low power cellular base station). The macro cellsinclude eNBs. The small cells include femtocells, picocells, andmicrocells.

The base stations 102 (collectively referred to as Evolved UniversalMobile Telecommunications System (UMTS) Terrestrial Radio Access Network(E-UTRAN)) interface with the EPC 160 through backhaul links 132 (e.g.,S1 interface). In addition to other functions, the base stations 102 mayperform one or more of the following functions: transfer of user data,radio channel ciphering and deciphering, integrity protection, headercompression, mobility control functions (e.g., handover, dualconnectivity), inter-cell interference coordination, connection setupand release, load balancing, distribution for non-access stratum (NAS)messages, NAS node selection, synchronization, radio access network(RAN) sharing, multimedia broadcast multicast service (MBMS), subscriberand equipment trace, RAN information management (RIM), paging,positioning, and delivery of warning messages. The base stations 102 maycommunicate directly or indirectly (e.g., through the EPC 160) with eachother over backhaul links 134 (e.g., X2 interface). The backhaul links134 may be wired or wireless.

The base stations 102 may wirelessly communicate with the UEs 104. Eachof the base stations 102 may provide communication coverage for arespective geographic coverage area 110. There may be overlappinggeographic coverage areas 110. For example, the small cell 102′ may havea coverage area 110′ that overlaps the coverage area 110 of one or moremacro base stations 102. A network that includes both small cell andmacro cells may be known as a heterogeneous network. A heterogeneousnetwork may also include Home Evolved Node Bs (eNBs) (HeNBs), which mayprovide service to a restricted group known as a closed subscriber group(CSG). The communication links 120 between the base stations 102 and theUEs 104 may include uplink (UL) (also referred to as reverse link)transmissions from a UE 104 to a base station 102 and/or downlink (DL)(also referred to as forward link) transmissions from a base station 102to a UE 104. The communication links 120 may use MIMO antennatechnology, including spatial multiplexing, beamforming, and/or transmitdiversity. The communication links may be through one or more carriers.The base stations 102/UEs 104 may use spectrum up to Y MHz (e.g., 5, 10,15, 20 MHz) bandwidth per carrier allocated in a carrier aggregation ofup to a total of Yx MHz (x component carriers) used for transmission ineach direction. The carriers may or may not be adjacent to each other.Allocation of carriers may be asymmetric with respect to DL and UL(e.g., more or less carriers may be allocated for DL than for UL). Thecomponent carriers may include a primary component carrier and one ormore secondary component carriers. A primary component carrier may bereferred to as a primary cell (PCell) and a secondary component carriermay be referred to as a secondary cell (SCell).

The wireless communications system may further include a Wi-Fi accesspoint (AP) 150 in communication with Wi-Fi stations (STAs) 152 viacommunication links 154 in a 5 GHz unlicensed frequency spectrum. Whencommunicating in an unlicensed frequency spectrum, the STAs 152/AP 150may perform a clear channel assessment (CCA) prior to communicating inorder to determine whether the channel is available.

The small cell 102′ may operate in a licensed and/or an unlicensedfrequency spectrum. When operating in an unlicensed frequency spectrum,the small cell 102′ may employ LTE and use the same 5 GHz unlicensedfrequency spectrum as used by the Wi-Fi AP 150. The small cell 102′,employing LTE in an unlicensed frequency spectrum, may boost coverage toand/or increase capacity of the access network. LTE in an unlicensedspectrum may be referred to as LTE-unlicensed (LTE-U), licensed assistedaccess (LAA), or MuLTEfire.

The EPC 160 may include a Mobility Management Entity (MME) 162, otherMMEs 164, a Serving Gateway 166, a Multimedia Broadcast MulticastService (MBMS) Gateway 168, a Broadcast Multicast Service Center (BM-SC)170, and a Packet Data Network (PDN) Gateway 172. The MME 162 may be incommunication with a Home Subscriber Server (HSS) 174. The MME 162 isthe control node that processes the signaling between the UEs 104 andthe EPC 160. Generally, the MME 162 provides bearer and connectionmanagement. All user Internet protocol (IP) packets are transferredthrough the Serving Gateway 166, which itself is connected to the PDNGateway 172. The PDN Gateway 172 provides UE IP address allocation aswell as other functions. The PDN Gateway 172 and the BM-SC 170 areconnected to the IP Services 176. The IP Services 176 may include theInternet, an intranet, an IP Multimedia Subsystem (IMS), a PS StreamingService (PSS), and/or other IP services. The BM-SC 170 may providefunctions for MBMS user service provisioning and delivery. The BM-SC 170may serve as an entry point for content provider MBMS transmission, maybe used to authorize and initiate MBMS Bearer Services within a publicland mobile network (PLMN), and may be used to schedule MBMStransmissions. The MBMS Gateway 168 may be used to distribute MBMStraffic to the base stations 102 belonging to a Multicast BroadcastSingle Frequency Network (MBSFN) area broadcasting a particular service,and may be responsible for session management (start/stop) and forcollecting eMBMS related charging information.

The base station may also be referred to as a Node B, evolved Node B(eNB), an access point, a base transceiver station, a radio basestation, a radio transceiver, a transceiver function, a basic serviceset (BSS), an extended service set (ESS), or some other suitableterminology. The base station 102 provides an access point to the EPC160 for a UE 104. Examples of UEs 104 include a cellular phone, a smartphone, a session initiation protocol (SIP) phone, a laptop, a personaldigital assistant (PDA), a satellite radio, a global positioning system,a multimedia device, a video device, a digital audio player (e.g., MP3player), a camera, a game console, a tablet, a smart device, a wearabledevice, or any other similar functioning device. The UE 104 may also bereferred to as a station, a mobile station, a subscriber station, amobile unit, a subscriber unit, a wireless unit, a remote unit, a mobiledevice, a wireless device, a wireless communications device, a remotedevice, a mobile subscriber station, an access terminal, a mobileterminal, a wireless terminal, a remote terminal, a handset, a useragent, a mobile client, a client, or some other suitable terminology.

Referring again to FIG. 1, in certain aspects, the UE 104 may beconfigured (198) to consider the travel speed of the UE 104 whendetermining a transmission configuration of the UE 104, to transmit thecontrol channel on one set of multiple sets of SA resources, and toenable group hopping for DM-RS sequences associated with the controlchannel for device-to-device communication. The device-to-devicecommunication may be vehicle-to-vehicle communication orvehicle-to-everything communication. Details of the operations performedat 198 will be further described below with references to FIGS. 2-13.

FIG. 2A is a diagram 200 illustrating an example of a DL frame structurein LTE. FIG. 2B is a diagram 230 illustrating an example of channelswithin the DL frame structure in LTE. FIG. 2C is a diagram 250illustrating an example of an UL frame structure in LTE. FIG. 2D is adiagram 280 illustrating an example of channels within the UL framestructure in LTE. Other wireless communication technologies may have adifferent frame structure and/or different channels. In LTE, a frame (10ms) may be divided into 10 equally sized subframes. Each subframe mayinclude two consecutive time slots. A resource grid may be used torepresent the two time slots, each time slot including one or more timeconcurrent resource blocks (RBs) (also referred to as physical RBs(PRBs)). The resource grid is divided into multiple resource elements(REs). In LTE, for a normal cyclic prefix, an RB contains 12 consecutivesubcarriers in the frequency domain and 7 consecutive symbols (for DL,OFDM symbols; for UL, SC-FDMA symbols) in the time domain, for a totalof 84 REs. For an extended cyclic prefix, an RB contains 12 consecutivesubcarriers in the frequency domain and 6 consecutive symbols in thetime domain, for a total of 72 REs. The number of bits carried by eachRE depends on the modulation scheme.

As illustrated in FIG. 2A, some of the REs carry DL reference (pilot)signals (DL-RS) for channel estimation at the UE. The DL-RS may includecell-specific reference signals (CRS) (also sometimes called common RS),UE-specific reference signals (UE-RS), and channel state informationreference signals (CSI-RS). FIG. 2A illustrates CRS for antenna ports 0,1, 2, and 3 (indicated as R₀, R₁, R₂, and R₃, respectively), UE-RS forantenna port 5 (indicated as R₅), and CSI-RS for antenna port 15(indicated as R). FIG. 2B illustrates an example of various channelswithin a DL subframe of a frame. The physical control format indicatorchannel (PCFICH) is within symbol 0 of slot 0, and carries a controlformat indicator (CFI) that indicates whether the physical downlinkcontrol channel (PDCCH) occupies 1, 2, or 3 symbols (FIG. 2B illustratesa PDCCH that occupies 3 symbols). The PDCCH carries downlink controlinformation (DCI) within one or more control channel elements (CCEs),each CCE including nine RE groups (REGs), each REG including fourconsecutive REs in an OFDM symbol. A UE may be configured with aUE-specific enhanced PDCCH (ePDCCH) that also carries DCI. The ePDCCHmay have 2, 4, or 8 RB pairs (FIG. 2B shows two RB pairs, each subsetincluding one RB pair). The physical hybrid automatic repeat request(ARQ) (HARQ) indicator channel (PHICH) is also within symbol 0 of slot 0and carries the HARQ indicator (HI) that indicates HARQ acknowledgement(ACK)/negative ACK (NACK) feedback based on the physical uplink sharedchannel (PUSCH). The primary synchronization channel (PSCH) is withinsymbol 6 of slot 0 within subframes 0 and 5 of a frame, and carries aprimary synchronization signal (PSS) that is used by a UE to determinesubframe timing and a physical layer identity. The secondarysynchronization channel (SSCH) is within symbol 5 of slot 0 withinsubframes 0 and 5 of a frame, and carries a secondary synchronizationsignal (SSS) that is used by a UE to determine a physical layer cellidentity group number. Based on the physical layer identity and thephysical layer cell identity group number, the UE can determine aphysical cell identifier (PCI). Based on the PCI, the UE can determinethe locations of the aforementioned DL-RS. The physical broadcastchannel (PBCH) is within symbols 0, 1, 2, 3 of slot 1 of subframe 0 of aframe, and carries a master information block (MIB). The MIB provides anumber of RBs in the DL system bandwidth, a PHICH configuration, and asystem frame number (SFN). The physical downlink shared channel (PDSCH)carries user data, broadcast system information not transmitted throughthe PBCH such as system information blocks (SIBs), and paging messages.

As illustrated in FIG. 2C, some of the REs carry demodulation referencesignals (DM-RS) for channel estimation at the eNB. The UE mayadditionally transmit sounding reference signals (SRS) in the lastsymbol of a subframe. The SRS may have a comb structure, and a UE maytransmit SRS on one of the combs. The SRS may be used by an eNB forchannel quality estimation to enable frequency-dependent scheduling onthe UL. FIG. 2D illustrates an example of various channels within an ULsubframe of a frame. A physical random access channel (PRACH) may bewithin one or more subframes within a frame based on the PRACHconfiguration. The PRACH may include six consecutive RB pairs within asubframe. The PRACH allows the UE to perform initial system access andachieve UL synchronization. A physical uplink control channel (PUCCH)may be located on edges of the UL system bandwidth. The PUCCH carriesuplink control information (UCI), such as scheduling requests, a channelquality indicator (CQI), a precoding matrix indicator (PMI), a rankindicator (RI), and HARQ ACK/NACK feedback. The PUSCH carries data, andmay additionally be used to carry a buffer status report (BSR), a powerheadroom report (PHR), and/or UCI.

FIG. 3 is a block diagram of an eNB 310 in communication with a UE 350in an access network. In the DL, IP packets from the EPC 160 may beprovided to a controller/processor 375. The controller/processor 375implements layer 3 and layer 2 functionality. Layer 3 includes a radioresource control (RRC) layer, and layer 2 includes a packet dataconvergence protocol (PDCP) layer, a radio link control (RLC) layer, anda medium access control (MAC) layer. The controller/processor 375provides RRC layer functionality associated with broadcasting of systeminformation (e.g., MIB, SIBs), RRC connection control (e.g., RRCconnection paging, RRC connection establishment, RRC connectionmodification, and RRC connection release), inter radio access technology(RAT) mobility, and measurement configuration for UE measurementreporting; PDCP layer functionality associated with headercompression/decompression, security (ciphering, deciphering, integrityprotection, integrity verification), and handover support functions; RLClayer functionality associated with the transfer of upper layer packetdata units (PDUs), error correction through ARQ, concatenation,segmentation, and reassembly of RLC service data units (SDUs),re-segmentation of RLC data PDUs, and reordering of RLC data PDUs; andMAC layer functionality associated with mapping between logical channelsand transport channels, multiplexing of MAC SDUs onto transport blocks(TBs), demultiplexing of MAC SDUs from TBs, scheduling informationreporting, error correction through HARQ, priority handling, and logicalchannel prioritization.

The transmit (TX) processor 316 and the receive (RX) processor 370implement layer 1 functionality associated with various signalprocessing functions. Layer 1, which includes a physical (PHY) layer,may include error detection on the transport channels, forward errorcorrection (FEC) coding/decoding of the transport channels,interleaving, rate matching, mapping onto physical channels,modulation/demodulation of physical channels, and MIMO antennaprocessing. The TX processor 316 handles mapping to signalconstellations based on various modulation schemes (e.g., binaryphase-shift keying (BPSK), quadrature phase-shift keying (QPSK),M-phase-shift keying (M-PSK), M-quadrature amplitude modulation(M-QAM)). The coded and modulated symbols may then be split intoparallel streams. Each stream may then be mapped to an OFDM subcarrier,multiplexed with a reference signal (e.g., pilot) in the time and/orfrequency domain, and then combined together using an Inverse FastFourier Transform (IFFT) to produce a physical channel carrying a timedomain OFDM symbol stream. The OFDM stream is spatially precoded toproduce multiple spatial streams. Channel estimates from a channelestimator 374 may be used to determine the coding and modulation scheme,as well as for spatial processing. The channel estimate may be derivedfrom a reference signal and/or channel condition feedback transmitted bythe UE 350. Each spatial stream may then be provided to a differentantenna 320 via a separate transmitter 318TX. Each transmitter 318TX maymodulate an RF carrier with a respective spatial stream fortransmission.

At the UE 350, each receiver 354RX receives a signal through itsrespective antenna 352. Each receiver 354RX recovers informationmodulated onto an RF carrier and provides the information to the receive(RX) processor 356. The TX processor 368 and the RX processor 356implement layer 1 functionality associated with various signalprocessing functions. The RX processor 356 may perform spatialprocessing on the information to recover any spatial streams destinedfor the UE 350. If multiple spatial streams are destined for the UE 350,they may be combined by the RX processor 356 into a single OFDM symbolstream. The RX processor 356 then converts the OFDM symbol stream fromthe time-domain to the frequency domain using a Fast Fourier Transform(FFT). The frequency domain signal comprises a separate OFDM symbolstream for each subcarrier of the OFDM signal. The symbols on eachsubcarrier, and the reference signal, are recovered and demodulated bydetermining the most likely signal constellation points transmitted bythe eNB 310. These soft decisions may be based on channel estimatescomputed by the channel estimator 358. The soft decisions are thendecoded and deinterleaved to recover the data and control signals thatwere originally transmitted by the eNB 310 on the physical channel. Thedata and control signals are then provided to the controller/processor359, which implements layer 3 and layer 2 functionality.

The controller/processor 359 can be associated with a memory 360 thatstores program codes and data. The memory 360 may be referred to as acomputer-readable medium. In the UL, the controller/processor 359provides demultiplexing between transport and logical channels, packetreassembly, deciphering, header decompression, and control signalprocessing to recover IP packets from the EPC 160. Thecontroller/processor 359 is also responsible for error detection usingan ACK and/or NACK protocol to support HARQ operations.

Similar to the functionality described in connection with the DLtransmission by the eNB 310, the controller/processor 359 provides RRClayer functionality associated with system information (e.g., MIB, SIBs)acquisition, RRC connections, and measurement reporting; PDCP layerfunctionality associated with header compression/decompression, andsecurity (ciphering, deciphering, integrity protection, integrityverification); RLC layer functionality associated with the transfer ofupper layer PDUs, error correction through ARQ, concatenation,segmentation, and reassembly of RLC SDUs, re-segmentation of RLC dataPDUs, and reordering of RLC data PDUs; and MAC layer functionalityassociated with mapping between logical channels and transport channels,multiplexing of MAC SDUs onto TBs, demultiplexing of MAC SDUs from TBs,scheduling information reporting, error correction through HARQ,priority handling, and logical channel prioritization.

Channel estimates derived by a channel estimator 358 from a referencesignal or feedback transmitted by the eNB 310 may be used by the TXprocessor 368 to select the appropriate coding and modulation schemes,and to facilitate spatial processing. The spatial streams generated bythe TX processor 368 may be provided to different antenna 352 viaseparate transmitters 354TX. Each transmitter 354TX may modulate an RFcarrier with a respective spatial stream for transmission.

The UL transmission is processed at the eNB 310 in a manner similar tothat described in connection with the receiver function at the UE 350.Each receiver 318RX receives a signal through its respective antenna320. Each receiver 318RX recovers information modulated onto an RFcarrier and provides the information to a RX processor 370.

The controller/processor 375 can be associated with a memory 376 thatstores program codes and data. The memory 376 may be referred to as acomputer-readable medium. In the UL, the controller/processor 375provides demultiplexing between transport and logical channels, packetreassembly, deciphering, header decompression, control signal processingto recover IP packets from the UE 350. IP packets from thecontroller/processor 375 may be provided to the EPC 160. Thecontroller/processor 375 is also responsible for error detection usingan ACK and/or NACK protocol to support HARQ operations.

FIG. 4 is a diagram of a device-to-device (D2D) communications system460. The D2D communications system 460 includes a plurality of UEs 464,466, 468, 470. The D2D communications system 460 may overlap with acellular communications system, such as for example, a WWAN. Some of theUEs 464, 466, 468, 470 may communicate together in D2D communicationusing the DL/UL WWAN spectrum, some may communicate with the basestation 462, and some may do both. For example, as shown in FIG. 4, theUEs 468, 470 are in D2D communication and the UEs 464, 466 are in D2Dcommunication. The UEs 464, 466 are also communicating with the basestation 462. The D2D communication may be through one or more sidelinkchannels, such as a physical sidelink broadcast channel (PSBCH), aphysical sidelink discovery channel (PSDCH), a physical sidelink sharedchannel (PSSCH), and a physical sidelink control channel (PSCCH).

The exemplary methods and apparatuses discussed infra are applicable toany of a variety of wireless D2D communications systems, such as forexample, a wireless device-to-device communication system based onFlashLinQ, WiMedia, Bluetooth, ZigBee, or Wi-Fi based on the IEEE 802.11standard. To simplify the discussion, the exemplary methods andapparatus are discussed within the context of LTE. However, one ofordinary skill in the art would understand that the exemplary methodsand apparatuses are applicable more generally to a variety of otherwireless device-to-device communication systems.

D2D communication over a licensed spectrum may be used to provide directcommunication between devices. One example of a D2D communication over alicensed spectrum includes communication using LTE Direct (LTE-D). D2Dcommunication enables one UE to communicate with another UE and transmitdata to the other UE over allocated resources. For example, UEs withinthe same network (e.g., within the same cell) or within a range witheach other may directly communicate with each other over a licensedspectrum via LTE-D. LTE-D may also be used to discover nearby UEs in thesame network. One application for the D2D communication over a licensedspectrum may be vehicle-to-vehicle (V2V) communication orvehicle-to-everything (V2X) communication. In V2V communication, a firstvehicle's UE may perform D2D communication with another vehicle's UEover the licensed spectrum. In V2X communication, a vehicle's UE mayperform D2D communication with another UE, regardless of whether theother UE resides in a vehicle or not, over the licensed spectrum.

During V2V communication (or V2X communication or D2D communication), acontrol channel and a data channel may be transmitted by a UE that wantsto communicate with another UE. A communication resource pool may beshared for the control channel and the data channel, e.g., someresources are allocated to the control channel and the rest of theresources are allocated to the data channel. The control channel may bea physical sidelink control channel (PSCCH). The control channel may bereferred to as a scheduling assignment (SA) channel because the controlchannel carries scheduling assignments. Each SA may indicate an MCSvalue and a location of resources in the data channel used to transmitdata. The transmitting UE may transmit encoded data on the data channelto another UE. The data channel may be transmitted after the controlchannel is transmitted. The data channel may be a physical sidelinkshared channel (PSSCH). When a UE wants to receive data from atransmitting UE, the control channel transmitted by the transmitting UEmay be decoded to determine resources used to transmit data for thetransmitting UE (e.g., where to look for in the data channel). Thereceiving UE may also determine the MCS for demodulating/decoding thedata based on the MCS value indicated in the control channel. Thus,based on the information in the control channel, the receiving UE maylocate the data in the resources configured for D2D communication, andmay subsequently be able to decode the data in the data channel.

A UE located in a vehicle may experience channel conditions that changequicker than stationary devices in that the channel conditions observedby the UE in the vehicle are affected by the speed of the vehicle'smovement. Thus, if a vehicle travels at a high speed, the UE in thevehicle also travels at a high speed. When traveling at high speed, thedevice's surrounding environment may change more rapidly, e.g., thenumber of reflections, the number of objects nearby, the Doppler spread,change more rapidly which in turn cause the communication channelconditions to change more rapidly. Rapidly changing channel conditionsmay result in less reliable channel estimation and reduce thereliability of channel decoding by the receiving UE. Aspects of thedisclosure relate to techniques for D2D (or V2V/V2X) communication whenthe speed of the UE is high (e.g., 250 km/h to 500 km/h). The D2D (orV2V/V2X) communication may be over licensed or unlicensed spectrum.

FIG. 5 is a diagram illustrating an example of a V2V communicationsystem 500. A first UE 512 is present in a first vehicle 510, and thusmay travel with the first vehicle 510. A second UE 532 may be present ina second vehicle 530 or may be present independently without the secondvehicle 530. The first UE 512 and the second UE 532 may be connected toa base station 550. The first UE 512 and the second UE 532 may beconfigured to perform D2D communication (e.g., V2V communication or V2Xcommunication) with each other. The D2D communication may be over alicensed or unlicensed spectrum. In the V2V communication system 500,the first UE 512 transmits data to the second UE 532 at 562. Thus, thefirst UE 512 may be referred to as a transmitting UE and the second UE532 may be referred to as a receiving UE.

According to an aspect of the disclosure, when the transmitting UE(e.g., the first UE 512) is traveling at a high speed, the channelestimation used during channel decoding (e.g., the control channel orthe data channel) by the receiving UE (e.g., the second UE 532) may beimproved by increasing redundancies in the channels transmitted by thetransmitting UE. In particular, the transmitting UE may estimate atravel speed (e.g., the absolute travel speed or the relative travelspeed) of the transmitting UE, and determine the transmissionconfiguration of the transmitting UE based on the speed of thetransmitting UE. In an aspect, the transmitting UE may adjust thetransmission configuration so that more redundancies in the channels aretransmitted if the transmitting UE is traveling at a high speed. Thetransmission configuration may include at least one of an MCS value(e.g., modulation order and/or coding rate), the number of RBs that thetransmitting UE uses for each (HARQ) transmission, and the number of(HARQ) retransmissions by the transmitting UE. For example, if thetravel speed of the transmitting UE is high, the transmissionconfiguration may be determined to have a lower MCS value and/or ahigher number of RBs used by the transmitting UE and/or a higher numberof retransmissions. For example, if the speed of the transmitting UE islow, the transmission configuration may be determined to have a higherMCS value and/or a lower number of RBs used by the transmitting UEand/or a lower number of retransmissions. In one example, thetransmitting UE may determine that the travel speed is high when thetravel speed exceeds a threshold, and may determine that the travelspeed is low when the travel speed does not exceed the threshold. In oneexample, the transmitting UE may determine that the travel speed is highwhen the travel speed increases to exceed a high threshold, and maydetermine that the travel speed is low when the travel speed decreasesto below a low threshold. A certain range of the travel speed may beassociated with a certain transmission configuration. That is, differentranges of travel speed may correspond to different transmissionconfigurations. The association of a travel speed and a transmissionconfiguration corresponding to the travel speed may be preconfiguredand/or may be signaled by the network (e.g., an eNB).

The transmission configuration may include an SA transmissionconfiguration and a data transmission configuration. Both the SAtransmission configuration and the data transmission configuration maybe determined based on the travel speed of the transmitting UE. Thetransmitting UE may transmit the control channel based on the SAtransmission configuration. The control channel may convey informationabout the data transmission configuration. The transmitting UE maytransmit the data channel based on the data transmission configuration.Further, after decoding the control channel received from thetransmitting UE, the receiving UE may receive the data channel from thetransmitting UE based on the data transmission configuration conveyed inthe control channel.

The transmitting UE may determine the travel speed based on the absolutetravel speed of the transmitting UE and/or characteristics of a regionwhere the transmitting UE is located. In an aspect, the travel speed maybe a travel speed estimated by the transmitting UE or a speedometerreading of the vehicle. In an aspect, the transmitting UE may determinea maximum speed of a region corresponding to the location of thetransmitting UE based on a speed limit of the region, where the locationof the transmitting UE may be estimated by a location sensor such as aglobal positioning system (GPS) device. For example, if a speed limit ofa road where the transmitting UE is located is 50 km/h, the transmittingUE may determine that the travel speed is 50 km/h. In an aspect, thetransmitting UE may determine whether a region corresponding to thelocation of the transmitting UE is a high speed region such as a highwayor a low speed region such as a local road. If the transmitting UE isdetermined to be located in a high speed region, the transmitting UE maydetermine that the travel speed is high. If the transmitting UE isdetermined to be located in a low speed region, the transmitting UE maydetermine that the travel speed is low.

In an aspect, the transmitting UE may receive information from anetwork, e.g., a LTE network or some other WWAN. The network may sendspeed limit information based on the current location of thetransmitting UE. The location of the UE may be determined by the GPSlocation information sent by the transmitting UE or may be determinedbased on the signal received at a base station from the transmitting UE.

As an example, in a typical configuration, a transmitting UE maytransmit 300 bytes of data over 20 RBs when moving at a low or mediumspeed. If the travel speed of the transmitting UE is high, the 300 bytesof data may be transmitted with a lower MCS, thus using more resources(e.g., 50 RBs). As an example, in a typical configuration, atransmitting UE may perform an SA transmission (e.g., via the controlchannel) over 1 RB when moving at a low or medium speed. If the travelspeed of the transmitting UE is high, redundancies may be added byrepetition of the SA transmission over 2 RBs. With sufficientredundancies, the receiving UE may successfully decode the controlchannel and the data channel even if the receiving UE does not have agood estimation of the channel conditions due to the high travel speed.For example, if the transmitting UE determines that the transmitting UEhas entered a high-speed area and/or is moving at a high speed (morethan 140 km/h) and thus the travel speed is high, the transmitting UEmay transmit the same amount (e.g., 300 bytes) of data with a lower MCS(e.g. over 50 RBs rather than 20 RBs).

FIG. 6 is an example plot 600 illustrating an error rate experienced bya UE in various situations. The example plot 600 shows a block errorrate versus signal to noise ratio (SNR) in V2V communication between atransmitting UE and a receiving UE when the transmitting UE is travelingat a speed of 250 km/h. The example plot 600 illustrates that, at a highspeed such as 250 km/h, using a typical MCS (e.g., transmitting 300bytes of data over 20 RBs) may result in a high block error rate (BLER)at the receiving UE regardless of the SNR at the receiving UE. Forexample, according to the example plot 600, at 250 km/h, if a typicalMCS (e.g., transmitting 300 bytes of data over 20 RBs) is used,achieving a low BLER of 10% may be difficult, regardless of whether adecision feedback (DF) algorithm is used. However, as the example plot600 illustrates, at 250 km/h, if 50 RBs are used (e.g., for a lower MCS)to transmit 300 bytes of data, a low BLER of 10% may be achieved for a2.5 dB SNR when the DF algorithm is used, and for a 5 dB SNR when the DFalgorithm is not used.

The complexity of the receiving UE may increase if different SAtransmission configurations are used to transmit SA channel. Forexample, the number of hypotheses (possible combinations of validcontrol channel resources) that have to be tested by the receiving UE todecode the control channel may increase (e.g., non-linearly) with thenumber of transmission configurations utilized. For example, if anavailable SA resource pool has 20 RBs per subframe and a typical SAtransmission is performed on 1 RB and an SA transmission for high speedis performed on 2 RBs, there may be 20 different hypotheses (20different possible combinations) for the typical SA transmission and 10different hypotheses for the high speed SA transmission, per subframe.In this example, the possibilities may be RB #0, RB #1, RB #2, . . . RB#19 for the typical SA transmission and RBs #0 #1, RBs #2 #3, RBs #4 #5,. . . RBs #18 #19. Thus, in this example, there may be 30 possible totalhypotheses per subframe. Therefore, an approach to reduce the complexityin channel decoding may be desirable.

According to an aspect of the disclosure, available SA resources may bedivided into multiple sets (e.g., N sets) of SA resources based on thetransmission configurations. The SA resources may be set aside fortransmission of a control channel, and every UE within a system mayutilize the same SA resources to transmit a control channel. Thus, a UEwanting to receive a communication from another UE may attempt to decodea control channel in the SA resources based on the hypotheses. In anaspect, a first set of resources may have a fixed transmissionconfiguration such that one blind decode may be used to detect thepresence of a control channel in the first set of SA resources. Thefirst set of SA resources may be used for a typical transmissionconfiguration, e.g., a low to medium speed for coexistence with legacydevices.

The size of each set of SA resources may depend on a travel speed of thetransmitting UE. Further, the type of SA transmission configurationassociated to each set of SA resources may depend on a travel speed ofthe transmitting UE. Different sets of SA resources may correspond todifferent travel speeds. The size and the SA transmission configurationfor each set of SA resources may be fixed, or preconfigured for arespective region, or may be signaled by a network (e.g., by an eNB).

In an aspect, a first set of multiple sets of SA resources may be usedto communicate with a fixed SA transmission configuration (e.g., fixedMCS and resource size) and may not be used to communicate with othertypes of SA transmission configurations. The first set of SA resourcesmay be used when the SA transmission configuration does not vary basedon the travel speed of the transmitting UE. Other sets (excluding thefirst set) of SA resources may be used by the transmitting UE tocommunicate using a configuration that varies according to the travelspeed of the transmitting UE. Thus, other sets of SA resources may beused when the transmitting UE travels at high speeds. Therefore, if thetransmitting UE determines to use the fixed SA transmissionconfiguration, the transmitting UE may transmit the control channelusing any one of the multiple sets of SA resources. If the transmittingUE determines to vary the SA transmission configuration based on thespeed of the transmitting UE, the transmitting UE may transmit thecontrol channel using a set of SA resources that is other than the firstset of SA resources. In one configuration, the set of SA resources usedmay correspond to the speed of the transmitting UE.

FIG. 7 is an example diagram 700 illustrating SA resources, according toan aspect of the disclosure. In this example, the SA resources mayinclude 10 subframes numbered 0 to 9. Each subframe may include a fixednumber of resource blocks, e.g., 12 RBs. As shown in the diagram 700,the SA resources may be divided into three sets of SA resourcesincluding Set 1, Set 2 and Set 3. Set 1 includes RBs for subframe number0 and 1, Set 2 includes RBs for subframe numbers 2, 3, 4, and 5, and Set3 includes RBs for subframe numbers 6, 7, 8, and 9. Set 1 may bededicated to a fixed SA transmission configuration. Set 2 may be used tocommunicate an SA transmission configuration when a travel speed of thetransmitting UE is a medium speed or may be used to communicate a fixedSA transmission configuration. Set 3 may be used to communicate an SAtransmission configuration when the travel speed of the transmitting UEis a high speed or may be used to communicate a fixed SA transmissionconfiguration. Thus, if the transmitting UE determines to use thetypical configuration with a fixed SA transmission configuration, thetransmitting UE may use any one of Set 1, Set 2 and Set 3 to communicatethe control channel. If the transmitting UE determines to use a varyingconfiguration based on the travel speed of the transmitting UE, thetransmitting UE may use Set 2 or Set 3 to communicate the controlchannel, depending on the travel speed of the transmitting UE. In anaspect, the transmitting UE may use Set 1 for the typical configurationof the SA transmission mode to reduce complexity at the receiving UE.

The receiving UE may receive transmissions from various transmittingUEs. The receiving UE may determine which set of SA resources is used totransmit a control channel by a transmitting UE. If the receiving UEreceives communication from the transmitting UE in one set of themultiple sets of SA resources, the receiving UE may attempt to decode(e.g., by blind decoding) a control channel from the set of SAresources, based on an SA transmission configuration for the controlchannel. Because the receiving UE may not attempt to decode from theentire SA resources, but may attempt to decode from a subset of SAresources, the complexity in decoding may be reduced. Further, forexample, Set 1 may be dedicated to the fixed SA transmissionconfiguration, and thus the hypotheses for Set 1 may be limited to thefixed SA transmission configuration, which reduces complexity indecoding. When the control channel is decoded, the receiving UE maydetermine a data transmission configuration based on the controlchannel. Subsequently, the receiving UE may receive data from thetransmitting UE based on the data transmission configuration. Forexample, referring to the example in FIG. 7, if the receiving UEdetermines that Set 1 is used to transmit SA, the receiving UE mayattempt to decode the control channel based on a fixed SA transmissionconfiguration from Set 1, and may not attempt to decode from Set 2 orSet 3. For example, referring to the example in FIG. 7, if the receivingUE determines that Set 3 is used to transmit SA, the receiving UE mayattempt to decode the control channel based on a fixed SA transmissionconfiguration and may also attempt to decode the control channel basedon an SA transmission configuration for high travel speed, from Set 3.In such an example, if the transmitting UE utilizes a varyingconfiguration based on the transmission, the receiving UE may end updecoding the control channel based on an SA transmission configurationfor high travel speed. If the transmitting UE utilizes a fixedconfiguration, the receiving UE may end up decoding the control channelbased on the fixed SA transmission configuration.

In one configuration, the fixed SA transmission configuration for atypical configuration may be defined based on the scenario (e.g., thegeographical region). For example, low to medium speed may be typical inan urban area, thus the fixed SA transmission configuration maycorrespond to the transmitting UE moving at low to medium speed.Similarly, high speed may be typical in a rural highway, thus the fixedSA transmission configuration may correspond to the transmitting UEmoving at high speed.

FIG. 8 is a flowchart 800 of a method of wireless communication,according to an aspect of the disclosure. The method may be performed bya UE (e.g., the UE 104, the first UE 512, the apparatus 1202/1202′).

At 802, the UE may determine a travel speed of the UE. In an aspect, thetravel speed may be determined based on at least one of the travel speedof the UE or a maximum travel speed corresponding to the location of theUE. In an aspect, the maximum travel speed corresponding to the locationof the UE may be determined by: determining the location of the UE, anddetermining the maximum travel speed corresponding to the location ofthe UE. In an aspect, the maximum travel speed corresponding to thelocation of the UE may be a speed limit of the area corresponding to thelocation of the UE. In an aspect, travel speed may be further determinedbased on a travel speed of the receiving UE.

At 804, the UE may determine, based on the travel speed of the UE, atransmission configuration of the UE for device-to-device communication.The D2D communication may be V2V communication or V2X communication. Thedevice-to-device communication may be over a licensed or unlicensedspectrum. In an aspect, the transmission configuration may include atleast one of an MCS, the number of resource blocks used fortransmission, and the number of retransmissions. In an aspect, theassociation between the travel speed and a corresponding transmissionconfiguration may be preconfigured or may be received from a basestation.

In an aspect, when the travel speed of the UE increases, the UE mayadjust the transmission configuration of the UE by performing at leastone of: increasing the number of resource blocks used for transmission,decreasing the modulation and coding scheme (MCS) value, or increasingthe number of retransmissions. In an aspect, when the travel speed ofthe UE decreases, the UE may adjust the transmission configuration ofthe UE by performing at least one of: decreasing the number of resourceblocks used for transmission, increasing the MCS value, or decreasingthe number of retransmissions.

At 806, the UE may transmit the device-to-device communication based onthe transmission configuration. In an aspect, the UE may transmit thedevice-to-device communication by transmitting an SA based on an SAtransmission configuration, and transmitting data via a data channelbased on a data transmission configuration. In such an aspect, the SAindicates the data transmission configuration and a location ofresources in the data channel for transmitting data.

In an aspect, the UE may transmit the device-to-device communication by:transmitting the SA on any one of a plurality of sets of SA resources ifthe UE determines to utilize a fixed SA transmission configuration, andtransmitting the SA on a corresponding set of SA resources other thanthe first set of SA resources if the UE determines to vary the SAtransmission configuration of the UE based on the travel speed of theUE. The available SA resources may be divided into the plurality of setsof SA resources based on types of SA transmission configurations. Insuch an aspect, the first set of SA resources may be associated with thefixed SA transmission configuration, and each of other sets of SAresources may be associated with a corresponding type of SA transmissionconfiguration and the fixed SA transmission configuration. In such anaspect, the size of each set of SA resources and at least one type of SAtransmission configuration for each set of SA resources may beassociated with a corresponding travel speed of the UE. In such anaspect, at least one of the size of each set of SA resources or the atleast one type of SA transmission configuration for each set of SAresources may be preconfigured or may be received from a base station.

FIG. 9 is a flowchart 900 of a method of wireless communication,according to an aspect of the disclosure. The method may be performed bya UE (e.g., the UE 104, the second UE 532, the apparatus 1202/1202′).

At 902, the UE may receive a communication from a transmitting UE via adevice-to-device communication. The device-to-device communication maybe over a licensed or unlicensed spectrum.

At 904, the UE may determine a corresponding set of SA resources used toreceive the communication from the transmitting UE among a plurality ofsets of SA resources. The available SA resources may be divided into theplurality of sets of SA resources based on types of SA transmissionconfigurations.

At 906, the UE may decode an SA based on the communication within thecorresponding set of SA resources. In an aspect, the UE may decode theSA indicating the data transmission configuration by blind decodingwithin the corresponding set of SA resources. In an aspect, the UE maydecode the SA based on a fixed SA configuration if the corresponding setof SA resources is the first set of SA resources, and may decode the SAbased on the fixed SA configuration or an SA transmission configurationassociated with the corresponding set of SA resources if thecorresponding set of SA resources is a set of SA resources differentfrom the first set.

At 908, the UE may determine a data transmission configuration based onthe SA within the corresponding set of SA resources.

At 910, the UE may receive a data transmission from the transmitting UEbased on the data transmission configuration. In an aspect, the datatransmission configuration may include at least one of an MCS, thenumber of resource blocks used for transmission, and the number ofretransmissions.

In an aspect, the UE may receive the data transmission by determining alocation of resources within the data channel based on the SA, andreceiving the data transmission based on the location of resources andthe data transmission configuration. In an aspect, the size of each setof SA resources and at least one type of SA transmission configurationfor each set of SA resources may be associated with a correspondingtravel speed of the transmitting UE. In such an aspect, at least one ofthe size of each set of SA resources or the at least one type of SAtransmission configuration for each set of SA resources may bepreconfigured or may be received from a base station.

Wireless networks may employ Zadoff-Chu sequences to orthogonalize orpseudo-orthogonalize wireless signals. A Zadoff-Chu sequence is acomplex-valued mathematical sequence which can be applied to a radiosignal and results in a substantially constant amplitude signal.Further, cyclic shifted versions of the Zadoff-Chu sequence and theradio signal are pseudo-orthogonal when received by a receiver. Agenerated Zadoff-Chu sequence that is not cyclic shifted is a rootsequence. In one configuration, each root sequence may be identified bya unique root index.

In one configuration, a subframe for D2D (or V2V/V2X) communication mayinclude multiple DM-RS symbols. Some of these DM-RS symbols may bewithin the control channel (e.g., PSCCH) of the subframe. Some of theseDM-RS symbols may be within the data channel (e.g., PSSCH) of thesubframe. A Zadoff-Chu sequence may be transmitted on each DM-RS symbolwithin a subframe. Such Zadoff-Chu sequence may be referred to as aDM-RS sequence. In one configuration, a DM-RS sequence may refer to asequence other than a Zadoff-Chu sequence. In one configuration, grouphopping may be enabled for DM-RS sequences of the control channel, suchthat within the control channel different DM-RS sequences aretransmitted on different DM-RS symbols. In one configuration, grouphopping may refer to hopping or changing the root indices of theZadoff-Chu sequences used for different DM-RS symbols. In oneconfiguration, enabling group hopping for DM-RS symbols within asubframe may resolve or alleviate the timing/frequency ambiguity issueencountered by vehicular D2D devices.

FIG. 10 is a diagram 1000 illustrating an example of enabling grouphopping for DM-RS symbols within a subframe. In this example, a subframefor D2D (or V2V/V2X) communication may include four DM-RS symbols 1002,1004, 1006, and 1008. The DM-RS symbols 1002, 1004, 1006, and 1008 arewithin the control channel (e.g., PSCCH) of the D2D or V2V/V2Xcommunication.

In one configuration, group hopping may be enabled for DM-RS symbolswithin the control channel. In such a configuration, the root indices ofthe Zadoff-Chu sequences used for the DM-RS symbols 1002, 1004, 1006,and 1008 may be different.

In one configuration, the DM-RS sequence used for each DM-RS symbolwithin the control channel may be determined at least in part based on agroup hopping pattern. In one configuration, a group hopping pattern maybe a pattern of different root indices for the Zadoff-Chu sequences usedfor different DM-RS symbols. In one configuration, the group hoppingpattern may be determined by the different root indices for theZadoff-Chu sequences used for different DM-RS symbols.

In one configuration, the root index of a Zadoff-Chu sequence for aDM-RS symbol may be a function of the time resource index. The timeresource index may refer to either slot index or symbol index of theDM-RS symbol. For example, the root index of the Zadoff-Chu sequence forthe DM-RS symbol 1002 may be a function of the slot index (e.g., “0”) ora function of the symbol index (e.g., “2”) of the DM-RS symbol 1002; andthe root index of the Zadoff-Chu sequence for the DM-RS symbol 1006 maybe a function of the slot index (e.g., “1”) or a function of the symbolindex (e.g., “8”) of the DM-RS symbol 1006.

In one configuration, the root index of a Zadoff-Chu sequence for aDM-RS symbol may be a function of the frequency resource index, withinthe scheduling assignment resource pool, used by the correspondingcontrol channel. For example, the root index of the Zadoff-Chu sequencefor the DM-RS symbol 1002 may be a function of the index of the firstresource block (RB) used by PSCCH of the subframe. Similarly, the rootindex of the Zadoff-Chu sequence for the DM-RS symbol 1004 may be afunction of the index of the first RB used by PSCCH of the subframe.

In one configuration, the root index of a Zadoff-Chu sequence for aDM-RS symbol may be a function of an identifier. The identifier may bedetermined at least in part based on an SA identifier associated withthe D2D or V2V/V2X communication. The identifier may provide somerandomization over the potentially interfering DM-RS transmissions fromdifferent UEs. In one configuration, the identifier may be fixed.

In one configuration, the UE in a D2D or V2V/V2X communication maydetermine to enable or disable group hopping for DM-RS symbols in thecontrol channel (e.g., PSCCH) based on one or more of: the speed of theUE, a pre-configuration, or a signaling from an eNB. For example, the UEmay determine to enable group hopping for DM-RS symbols in the controlchannel when its speed is faster than or equal to a threshold (e.g., 140km/h), and the UE may determine to disable group hopping for DM-RSsymbols in the control channel when its speed is slower than thethreshold. The UE may determine its speed using methods described abovewith reference to FIG. 5.

In one configuration, the UE in a D2D or V2V/V2X communication may applya group hopping pattern to DM-RS symbols in the data channel (e.g.,PSSCH). In one configuration, the group hopping pattern applied to theDM-RS symbols in the data channel may be similar to the group hoppingpattern described above for the DM-RS symbols of the control channel. Inone configuration, the group hopping pattern applied to the DM-RSsymbols in the data channel may be a function of the symbol index of theDM-RS symbol. Using the symbol index of the DM-RS symbol to determinethe root index of the Zadoff-Chu sequence for the DM-RS symbol may makeit highly likely that all DM-RS symbols transmitted within the subframeare different (e.g., using different root indices). In oneconfiguration, the group hopping pattern applied to the DM-RS symbols inthe data channel may be a function of the slot index of the DM-RSsymbol.

FIG. 11 is a flowchart 1100 of a method of wireless communication inaccordance with an aspect of the disclosure. Specifically, this figureillustrates a method of enabling grouping hopping for DM-RS symbolswithin a control channel for D2D or V2V/V2X communication. The methodmay be performed by a UE (e.g., the UE 104, the first UE 512, the secondUE 532, or the apparatus 1202/1202′).

At 1102, the UE may determine to enable group hopping for a plurality ofDM-RS sequences associated with a control channel (e.g., PSCCH) fordevice-to-device communication. The plurality of DM-RS sequences may becarried on a plurality of DM-RS symbols (e.g., 1002, 1004, 1006, and1008) within the control channel of a subframe. In one configuration,the determination of enabling group hopping may be based on one or moreof a travel speed of the UE, a pre-configuration, or an eNB signaling.In one configuration, different DM-RS sequences may be carried ondifferent DM-RS symbols.

At 1104, the UE may determine the plurality of DM-RS sequences byapplying a group hopping pattern to the plurality of DM-RS symbols. Inone configuration, the plurality of DM-RS sequences may be generatedbased on Zadoff-Chu sequences. In one configuration, to apply the grouphopping pattern to the plurality of DM-RS symbols, the UE changes rootindices of the Zadoff-Chu sequences used for different DM-RS symbols.

In one configuration, a root index of a Zadoff-Chu sequence used for aDM-RS symbol of the plurality of DM-RS symbols may be determined basedon a time resource index. In one configuration, the time resource indexmay be a slot index of the DM-RS symbol or a symbol index of the DM-RSsymbol. In one configuration, the root index of the Zadoff-Chu sequenceused for the DM-RS symbol may be determined further based on a frequencyresource index used by the control channel. In one configuration, theroot index of the Zadoff-Chu sequence used for the DM-RS symbol may bedetermined further based on an identifier. In one configuration, theidentifier may be determined based at least in part on a schedulingassignment identifier associated with the device-to-devicecommunication. In another configuration, the identifier may be a fixedidentifier.

At 1106, the UE may transmit or receive a scheduling assignment for thedevice-to-device communication along with the plurality of DM-RSsequences.

At 1108, the UE may optionally determine a second plurality of DM-RSsequences associated with a data channel (e.g., PSSCH) for thedevice-to-device communication by applying a second group hoppingpattern to a second plurality of DM-RS symbols within the data channelof the subframe. In one configuration, the second plurality of DM-RSsequences may be generated based on Zadoff-Chu sequences. In oneconfiguration, to apply the second group hopping pattern to the secondplurality of DM-RS symbols, the UE may change root indices of theZadoff-Chu sequences used for different DM-RS symbols. In oneconfiguration, a root index of a Zadoff-Chu sequence used for a DM-RSsymbol of the second plurality of DM-RS symbols may be determined basedon a slot index of the DM-RS symbol.

At 1110, the UE may optionally transmit or receive data for thedevice-to-device communication with the second plurality of DM-RSsequences.

FIG. 12 is a conceptual data flow diagram 1200 illustrating the dataflow between different means/components in an exemplary apparatus 1202.The apparatus may be a UE. The apparatus includes a reception component1204, a transmission component 1206, and a travel speed component 1208,a transmission configuration component 1210, a communication managementcomponent 1212, a decoding component 1214, and a group hopping component1216. The apparatus 1202 and a second UE 1240 may be connected to a basestation 1250 at 1262, 1264, and 1266.

According to one aspect, the apparatus 1202 may be a UE that transmitsor receives communication to or from other devices (e.g., the second UE1240). In this aspect, the travel speed component 1208 may determine atravel speed of the apparatus 1202. The travel speed component 1208 mayconvey information about the travel speed to the transmissionconfiguration component 1210, at 1268. The travel speed component 1208may convey information about the travel speed to the group hoppingcomponent 1216, at 1284. In an aspect, the travel speed may bedetermined based on at least one of the travel speed of the apparatus1202 or the maximum travel speed corresponding to a location of theapparatus 1202. In an aspect, the travel speed component 1208 maydetermine the maximum travel speed corresponding to the location of theapparatus 1202 by: determining a location of the apparatus 1202, anddetermining the maximum travel speed corresponding to the location ofthe apparatus 1202. In an aspect, the maximum travel speed correspondingto the location of the apparatus 1202 may be the speed limit of an areacorresponding to the location of the apparatus 1202. In an aspect,travel speed may be further determined based on the travel speed of areceiving UE (e.g., the UE 1240).

The transmission configuration component 1210 may determine, based onthe travel speed of the UE, a transmission configuration of theapparatus 1202 for device-to-device communication. The device-to-devicecommunication may be over a licensed or unlicensed spectrum. Thetransmission configuration component 1210 may convey information aboutthe transmission configuration to the communication management component1212, at 1270. In an aspect, the transmission configuration may includeat least one of an MCS, the number of resource blocks used fortransmission, and the number of retransmissions. In an aspect,association information of the travel speed and a correspondingtransmission configuration may be preconfigured or may be received froma base station (e.g., the base station 1250).

In an aspect, when the travel speed of the apparatus 1202 increases(e.g., according to the travel speed component 1208), the transmissionconfiguration component 1210 may adjust the transmission configurationof the UE by performing at least one of: increasing a number of resourceblocks used for transmission, decreasing a modulation and coding scheme(MCS) value, or increasing a number of retransmissions. In an aspect,when the travel speed of the UE decreases (e.g., according to the travelspeed component 1208), the transmission configuration component 1210 mayadjust the transmission configuration of the UE by performing at leastone of: decreasing a number of resource blocks used for transmission,increasing an MCS value, or decreasing a number of retransmissions.

The group hopping component 1216 enables or disables, based on thetravel speed of the UE, group hopping for DM-RS symbols within a controlchannel for device-to-device communication. The group hopping component1216 may convey information about the group hopping to the communicationmanagement component 1212, at 1286. In an aspect, the enabling/disablingof group hopping may be preconfigured or may be received from a basestation (e.g., the base station 1250).

In an aspect, when the travel speed of the UE increases (e.g., accordingto the travel speed component 1208), the group hopping component 1216may enable group hopping. In an aspect, when the travel speed of the UEdecreases (e.g., according to the travel speed component 1208), thegroup hopping component 1216 may disable group hopping.

The communication management component 1212 may transmit, via thetransmission component 1206, the device-to-device communication based onthe transmission configuration (e.g., to a second UE 1240) and/or thegroup hopping configuration (e.g., enabled or disabled), at 1272 and1274.

In an aspect, the communication management component 1212 may transmit,via the transmission component 1206, the device-to-device communicationby transmitting an SA based on an SA transmission configuration, and maytransmit the data via a data channel based on a data transmissionconfiguration. In such an aspect, the SA may indicate the datatransmission configuration and a location of resources for the datachannel.

In an aspect, the communication management component 1212 may transmit,via the transmission component 1206, the device-to-device communicationby: transmitting the SA on any one of a plurality of sets of SAresources if the communication management component 1212 determines toutilize a fixed SA transmission configuration, and transmitting the SAon a corresponding set of SA resources other than a first set of SAresources if the communication management component 1212 determines tovary the SA transmission configuration of the UE based on the travelspeed of the UE. The SA resources may be divided into the plurality ofsets of SA resources based on types of SA transmission configurations.In such an aspect, the first set of SA resources may be associated withthe fixed SA transmission configuration, and each of other sets of SAresources may be associated with a corresponding type of SA transmissionconfiguration and the fixed SA transmission configuration. In such anaspect, the size of each set of SA resources and at least one type of SAtransmission configuration for each set of SA resources may beassociated with a corresponding travel speed of the UE. In such anaspect, at least one of the size of each set of SA resources or the atleast one type of SA transmission configuration for each set of SAresources may be preconfigured or may be received from a base station(e.g., base station 1250).

According to one aspect, the apparatus 1202 may be a receiving UE thatreceives communication from a transmitting UE. In this aspect, thecommunication management component 1212 may receive, via the receptioncomponent 1204, communication from a transmitting UE (e.g., second UE1240) via device-to-device communication, at 1276 and 1278.

The communication management component 1212 may determine acorresponding set of SA resources used to receive the communication fromthe transmitting UE (e.g., second UE 1240) among a plurality of sets ofSA resources. The SA resources may be divided into the plurality of setsof SA resources based on types of SA transmission configurations. Thecommunication management component 1212 may convey information about thecorresponding set of SA resources to the decoding component 1214, at1280. In one configuration, the communication management component 1212may perform channel estimation based on the DM-RS sequences receivedfrom the group hopping component 1216.

The decoding component 1214 decodes an SA based on the communicationwithin the corresponding set of SA resources. The decoding component1214 may convey information about the SA to the transmissionconfiguration component 1210, at 1282.

In an aspect, the decoding component 1214 may decode the SA by blinddecoding within the corresponding set of SA resources to decode the SAindicating the data transmission configuration.

In an aspect, the decoding component 1214 may decode the SA by decodingfor an SA based on a fixed SA configuration if the corresponding set ofSA resources is a first set of SA resources, and decoding for an SAbased on the fixed SA configuration or an SA based on an SA transmissionconfiguration corresponding to the corresponding set of SA resources ifthe corresponding set of SA resources is a set of SA resources differentfrom the first set.

The transmission configuration component 1210 may determine a datatransmission configuration based on the SA within the corresponding setof SA resources. The transmission configuration component 1210 mayconvey information about the data transmission configuration to thecommunication management component 1212, at 1970.

The communication management component 1212 may receive, via thereception component 1204, data from the transmitting UE (e.g., second UE1240) based on the data transmission configuration, at 1276 and 1278.

In an aspect, the data transmission configuration may include at leastone of an MCS, a number of resource blocks used for transmission, and anumber of retransmissions.

In an aspect, the communication management component 1212 may receivethe data (e.g., from the second UE 1240) by determining a location ofresources for the data channel based on the SA, and receiving the databased on the location of resources for the data channel and the datatransmission configuration.

In an aspect, the size of each set of SA resources and at least one typeof SA transmission configuration for each set of SA resources may beassociated with a corresponding travel speed of the transmitting UE(e.g., second UE 1240). In such an aspect, at least one of the size ofeach set of SA resources or the at least one type of SA transmissionconfiguration for each set of SA resources may be preconfigured or maybe received from a base station.

The apparatus may include additional components that perform each of theblocks of the algorithm in the aforementioned flowcharts of FIGS. 8, 9,and 11. As such, each block in the aforementioned flowcharts of FIGS. 8,9, and 11 may be performed by a component and the apparatus may includeone or more of those components. The components may be one or morehardware components specifically configured to carry out the statedprocesses/algorithm, implemented by a processor configured to performthe stated processes/algorithm, stored within a computer-readable mediumfor implementation by a processor, or some combination thereof.

FIG. 13 is a diagram 1300 illustrating an example of a hardwareimplementation for an apparatus 1202′ employing a processing system1314. The processing system 1314 may be implemented with a busarchitecture, represented generally by the bus 1324. The bus 1324 mayinclude any number of interconnecting buses and bridges depending on thespecific application of the processing system 1314 and the overalldesign constraints. The bus 1324 links together various circuitsincluding one or more processors and/or hardware components, representedby the processor 1304, the components 1204, 1206, 1208, 1210, 1212,1214, 1216, and the computer-readable medium/memory 1306. The bus 1324may also link various other circuits such as timing sources,peripherals, voltage regulators, and power management circuits, whichare well known in the art, and therefore, will not be described anyfurther.

The processing system 1314 may be coupled to a transceiver 1310. Thetransceiver 1310 is coupled to one or more antennas 1320. Thetransceiver 1310 provides a means for communicating with various otherapparatus over a transmission medium. The transceiver 1310 receives asignal from the one or more antennas 1320, extracts information from thereceived signal, and provides the extracted information to theprocessing system 1314, specifically the reception component 1204. Inaddition, the transceiver 1310 receives information from the processingsystem 1314, specifically the transmission component 1206, and based onthe received information, generates a signal to be applied to the one ormore antennas 1320. The processing system 1314 includes a processor 1304coupled to a computer-readable medium/memory 1306. The processor 1304 isresponsible for general processing, including the execution of softwarestored on the computer-readable medium/memory 1306. The software, whenexecuted by the processor 1304, causes the processing system 1314 toperform the various functions described supra for any particularapparatus. The computer-readable medium/memory 1306 may also be used forstoring data that is manipulated by the processor 1304 when executingsoftware. The processing system 1314 further includes at least one ofthe components 1204, 1206, 1208, 1210, 1212, 1214, 1216. The componentsmay be software components running in the processor 1304,resident/stored in the computer readable medium/memory 1306, one or morehardware components coupled to the processor 1304, or some combinationthereof. The processing system 1314 may be a component of the UE 350 andmay include the memory 360 and/or at least one of the TX processor 368,the RX processor 356, and the controller/processor 359.

In one configuration, the apparatus 1202/1202′ for wirelesscommunication may include means for determining a travel speed of theUE, means for determining, based on the travel speed of the UE, atransmission configuration of the UE for device-to-device communication,and means for transmitting the device-to-device communication based onthe transmission configuration. In an aspect, when the travel speed ofthe UE increases, the means for determining may be configured to performat least one of: increasing a number of resource blocks used fortransmission, decreasing an MCS value, or increasing a number ofretransmissions. In an aspect, when the travel speed of the UEdecreases, the means for determining may be configured to perform atleast one of: decreasing a number of resource blocks used fortransmission, increasing an MCS value, or decreasing a number ofretransmissions. In an aspect, the means for transmitting of thedevice-to-device communication may be configured to: transmit an SAbased on an SA transmission configuration, and transmit the data via adata channel based on a data transmission configuration. In an aspect,the means for transmitting of the device-to-device communication may beconfigured to: transmit the SA on any one of a plurality of sets of SAresources if the UE determines to utilize a fixed SA transmissionconfiguration, and transmit the SA on a corresponding set of SAresources other than a first set of SA resources if the UE determines tovary the SA transmission configuration of the UE based on the travelspeed of the UE, where the SA resources are divided into the pluralityof sets of SA resources based on types of SA transmissionconfigurations.

In another configuration, the apparatus 1202/1202′ for wirelesscommunication may include means for receiving communication from atransmitting UE via device-to-device communication, means fordetermining a corresponding set of SA resources used to receive thecommunication from the transmitting UE among a plurality of sets of SAresources, where the SA resources are divided into the plurality of setsof SA resources based on types of SA transmission configurations, meansfor decoding an SA based on the communication within the correspondingset of SA resources, means for determining a data transmissionconfiguration based on the SA within the corresponding set of SAresources, and means for receiving data from the transmitting UE basedon the data transmission configuration. In an aspect, the means fordecoding the SA may be configured to perform blind decoding within thecorresponding set of SA resources to decode the SA indicating the datatransmission configuration. In an aspect, the means for decoding the SAmay be configured to: decode for an SA based on a fixed SA configurationif the corresponding set of SA resources is a first set of SA resources,and decode for an SA based on the fixed SA configuration or an SA basedon an SA transmission configuration corresponding to the correspondingset of SA resources if the corresponding set of SA resources is a set ofSA resources different from the first set. In an aspect, the means forreceiving the data may be configured to: determine a location ofresources for the data channel based on the SA, and receive the databased on the location of resources for the data channel and the datatransmission configuration.

In one configuration, the apparatus 1202/1202′ for wirelesscommunication may include means for determining to enable group hoppingfor a plurality of DM-RS sequences associated with a control channel fordevice-to-device communication, means for determining the plurality ofDM-RS sequences by applying a group hopping pattern to the plurality ofDM-RS symbols, and means for transmitting or receiving schedulingassignment for the device-to-device communication with the plurality ofDM-RS sequences. In one configuration, the means for determining toenable group hopping may be configured to operate based on one or moreof a travel speed of the apparatus, a pre-configuration, or an eNBsignaling. In one configuration, to apply the group hopping pattern tothe plurality of DM-RS symbols, the means for determining the pluralityof DM-RS sequences may be configured to change root indices of theZadoff-Chu sequences used for different DM-RS symbols.

In one configuration, the apparatus 1202/1202′ may include means fordetermining a second plurality of DM-RS sequences associated with a datachannel for the device-to-device communication by applying a secondgroup hopping pattern to a second plurality of DM-RS symbols within thedata channel of the subframe. In one configuration, to apply the secondgroup hopping pattern to the second plurality of DM-RS symbols, themeans for determining a second plurality of DM-RS sequences may beconfigured to change root indices of the Zadoff-Chu sequences used fordifferent DM-RS symbols.

In one configuration, the apparatus 1202/1202′ may include means fortransmitting or receiving data for the device-to-device communicationwith the second plurality of DM-RS sequences.

The aforementioned means may be one or more of the aforementionedcomponents of the apparatus 1202 and/or the processing system 1314 ofthe apparatus 1202′ configured to perform the functions recited by theaforementioned means. As described supra, the processing system 1314 mayinclude the TX Processor 368, the RX Processor 356, and thecontroller/processor 359. As such, in one configuration, theaforementioned means may be the TX Processor 368, the RX Processor 356,and the controller/processor 359 configured to perform the functionsrecited by the aforementioned means.

It is understood that the specific order or hierarchy of blocks in theprocesses/flowcharts disclosed is an illustration of exemplaryapproaches. Based upon design preferences, it is understood that thespecific order or hierarchy of blocks in the processes/flowcharts may berearranged. Further, some blocks may be combined or omitted. Theaccompanying method claims present elements of the various blocks in asample order, and are not meant to be limited to the specific order orhierarchy presented.

The previous description is provided to enable any person skilled in theart to practice the various aspects described herein. Variousmodifications to these aspects will be readily apparent to those skilledin the art, and the generic principles defined herein may be applied toother aspects. Thus, the claims are not intended to be limited to theaspects shown herein, but is to be accorded the full scope consistentwith the language claims, wherein reference to an element in thesingular is not intended to mean “one and only one” unless specificallyso stated, but rather “one or more.” The word “exemplary” is used hereinto mean “serving as an example, instance, or illustration.” Any aspectdescribed herein as “exemplary” is not necessarily to be construed aspreferred or advantageous over other aspects. Unless specifically statedotherwise, the term “some” refers to one or more. Combinations such as“at least one of A, B, or C,” “one or more of A, B, or C,” “at least oneof A, B, and C,” “one or more of A, B, and C,” and “A, B, C, or anycombination thereof” include any combination of A, B, and/or C, and mayinclude multiples of A, multiples of B, or multiples of C. Specifically,combinations such as “at least one of A, B, or C,” “one or more of A, B,or C,” “at least one of A, B, and C,” “one or more of A, B, and C,” and“A, B, C, or any combination thereof” may be A only, B only, C only, Aand B, A and C, B and C, or A and B and C, where any such combinationsmay contain one or more member or members of A, B, or C. All structuraland functional equivalents to the elements of the various aspectsdescribed throughout this disclosure that are known or later come to beknown to those of ordinary skill in the art are expressly incorporatedherein by reference and are intended to be encompassed by the claims.Moreover, nothing disclosed herein is intended to be dedicated to thepublic regardless of whether such disclosure is explicitly recited inthe claims. The words “module,” “mechanism,” “element,” “device,” andthe like may not be a substitute for the word “means.” As such, no claimelement is to be construed as a means plus function unless the elementis expressly recited using the phrase “means for.”

What is claimed is:
 1. A method for wireless communication performed bya user equipment (UE), the method comprising: receiving a communicationfrom a transmitting UE via device-to-device communication; determining acorresponding set of scheduling assignment (SA) resources used toreceive the communication from the transmitting UE among a plurality ofsets of SA resources, wherein SA resources are divided into theplurality of sets of SA resources based on types of SA transmissionconfigurations; decoding an SA based on the communication within thecorresponding set of SA resources; determining a data transmissionconfiguration based on the SA within the corresponding set of SAresources; and receiving data from the transmitting UE based on the datatransmission configuration.
 2. The method of claim 1, wherein thedecoding the SA comprises: performing blind decoding within thecorresponding set of SA resources to decode the SA indicating the datatransmission configuration.
 3. The method of claim 1, wherein thedecoding the SA comprises: decoding for an SA based on a fixed SAconfiguration if the corresponding set of SA resources is a first set ofSA resources; and decoding for an SA based on the fixed SA configurationor an SA based on an SA transmission configuration corresponding to thecorresponding set of SA resources if the corresponding set of SAresources is a set of SA resources different from the first set of SAresources.
 4. The method of claim 1, wherein the data transmissionconfiguration includes at least one of a modulation and coding scheme(MCS), a number of resource blocks used for transmission, and a numberof retransmissions.
 5. The method of claim 1, wherein the receiving thedata comprises: determining a location of resources for a data channelbased on the SA; and receiving the data based on the location ofresources for the data channel and the data transmission configuration.6. The method of claim 1, wherein a size of each set of SA resources andat least one type of SA transmission configuration for each set of SAresources is associated with a corresponding travel speed of thetransmitting UE.
 7. The method of claim 6, wherein at least one of thesize of each set of SA resources or the at least one type of SAtransmission configuration for each set of SA resources is preconfiguredor is received from a base station.
 8. An apparatus for wirelesscommunication by a user equipment (UE), the apparatus comprising: meansfor receiving communication from a transmitting UE via device-to-devicecommunication; means for determining a corresponding set of schedulingassignment (SA) resources used to receive the communication from thetransmitting UE among a plurality of sets of SA resources, wherein SAresources are divided into the plurality of sets of SA resources basedon types of SA transmission configurations; means for decoding an SAbased on the communication within the corresponding set of SA resources;means for determining a data transmission configuration based on the SAwithin the corresponding set of SA resources; and means for receivingdata from the transmitting UE based on the data transmissionconfiguration.
 9. The apparatus of claim 8, wherein the means fordecoding the SA is configured to: perform blind decoding within thecorresponding set of SA resources to decode the SA indicating the datatransmission configuration.
 10. The apparatus of claim 8, wherein themeans for decoding the SA is configured to: decode for an SA based on afixed SA configuration if the corresponding set of SA resources is afirst set of SA resources; and decode for an SA based on the fixed SAconfiguration or an SA based on an SA transmission configurationcorresponding to the corresponding set of SA resources if thecorresponding set of SA resources is a set of SA resources differentfrom the first set of SA resources.
 11. The apparatus of claim 8,wherein the data transmission configuration includes at least one of amodulation and coding scheme (MCS), a number of resource blocks used fortransmission, and a number of retransmissions.
 12. The apparatus ofclaim 8, wherein the means for receiving the data is configured to:determine a location of resources for a data channel based on the SA;and receive the data based on the location of resources for the datachannel and the data transmission configuration.
 13. The apparatus ofclaim 8, wherein a size of each set of SA resources and at least onetype of SA transmission configuration for each set of SA resources isassociated with a corresponding travel speed of the transmitting UE. 14.The apparatus of claim 13, wherein at least one of the size of each setof SA resources or the at least one type of SA transmissionconfiguration for each set of SA resources is preconfigured or isreceived from a base station.
 15. An apparatus for wirelesscommunication at a user equipment (UE), the apparatus comprising: amemory; and at least one processor coupled to the memory and configuredto: receive a communication from a transmitting UE via device-to-devicecommunication; determine a corresponding set of scheduling assignment(SA) resources used to receive the communication from the transmittingUE among a plurality of sets of SA resources, wherein SA resources aredivided into the plurality of sets of SA resources based on types of SAtransmission configurations; decode an SA based on the communicationwithin the corresponding set of SA resources; determine a datatransmission configuration based on the SA within the corresponding setof SA resources; and receive data from the transmitting UE based on thedata transmission configuration.
 16. The apparatus of claim 15, whereinthe at least one processor to decode the SA is configured to: performblind decoding within the corresponding set of SA resources to decodethe SA indicating the data transmission configuration.
 17. The apparatusof claim 15, wherein the at least one processor to decode the SA isconfigured to: decode for an SA based on a fixed SA configuration if thecorresponding set of SA resources is a first set of SA resources; anddecode for an SA based on the fixed SA configuration or an SA based onan SA transmission configuration corresponding to the corresponding setof SA resources if the corresponding set of SA resources is a set of SAresources different from the first set of SA resources.
 18. Theapparatus of claim 15, wherein the data transmission configurationincludes at least one of a modulation and coding scheme (MCS), a numberof resource blocks used for transmission, and a number ofretransmissions.
 19. The apparatus of claim 15, wherein the at least oneprocessor to receive the data is configured to: determine a location ofresources for a data channel based on the SA; and receive the data basedon the location of resources for the data channel and the datatransmission configuration.
 20. The apparatus of claim 15, wherein asize of each set of SA resources and at least one type of SAtransmission configuration for each set of SA resources is associatedwith a corresponding travel speed of the transmitting UE.
 21. Theapparatus of claim 20, wherein at least one of the size of each set ofSA resources or the at least one type of SA transmission configurationfor each set of SA resources is preconfigured or is received from a basestation.
 22. A computer-readable medium for a user equipment (UE)storing computer executable code, comprising code to: receivecommunication from a transmitting UE via device-to-device communication;determine a corresponding set of scheduling assignment (SA) resourcesused to receive the communication from the transmitting UE among aplurality of sets of SA resources, wherein SA resources are divided intothe plurality of sets of SA resources based on types of SA transmissionconfigurations; decode an SA based on the communication within thecorresponding set of SA resources; determine a data transmissionconfiguration based on the SA within the corresponding set of SAresources; and receive data from the transmitting UE based on the datatransmission configuration.